Method and apparatus for the melt extrusion of artificial materials



March 16, 1948. I R. w. MONCRIEFF ETAL METHOD AND APPARATUS FOR THE MELT EXTRUSION OF ARTIFICIAL MATERIALS 3 sheets -sheet 1 Filed Dec. 6, 1944 J FIG] I nvenlor; mwMowr/sn:

W-PoaL. W 7

Attorney;

March 16, 1948. R. w. MONCRIEFF ETAL 2,437,704

METHOD AND APPARATUS FOR MELT EXTRUSION OF ARTIFICIAL MATERIALS Filed Dec. 6, 1944 3 Sheets-Sheet 2 A llorney Bv .6 r

March 16, 1948 R. w. MONCRIEFF ETAL 2,437,704

METHOD AND APPARATUS FOR THE MELT EXTRUSION 0F ARTIFICIAL MATERIALS Filed Dec. 6, 1944 3 Sheets-Shqet 3 Patented Mar. 16, 1948 METHOD AND APPARATUS FOR MELT EXTRUSION OF ARTIFICIAL MATERIALS' Robert Wighton Moncriei! and William Pool, Spondon, near Derby, England, assignors, by mesne assignments, to Celanese Corporation of America, a corporation of Delaware Application December a, 1944, Serial No. 566,901. In Great Britain November 24, 1943 Section 1, Public Law 09o. August a, 1946 Patent expires November 24, 1963 16 Claims. ('01. 18-8) This invention relates to the production of artificial filaments, foils, films and like materials and particularly to the production of artificial materials by the extrusion of fused thermoplastic compositions.

In one method of extruding fused thermoplastic compositions to form artificial, filaments, foils, films and the like, solid thermoplastic composition is introduced into a closed vessel and is melted therein so as to form a pool or reservoir of molten composition, from which the composition is drawn and forced through orifices of appropriate size and shape into the form of filaments or the like. Extrusion may be effected either by means of a pump fed from the pool of molten composition, or by the pressure of an inert gas supplied to the vessel in which melting takes place, or by the use of a pump assisted by the pressure of such inert gas. In its simplest aspect the method comprises introducing a single charge of solid composition into the vessel and, when a sufficient part thereof has melted to constitute a reservoir of molten composition. spinning proceeds simultaneously with the melting of the rest of the composition and continues until the charge in the vessel is exhausted. Preferably, however. the vessel is supplied with fresh solid composition during the spinning operation so that the spinning operation continues indefinitely. Diiiiculties arise however in the introduction of the solid composition for this purpose. Thus for example it is necessary to avoid releasing the pressure of inert gas within the vessel during the 2 volved in effecting this double sealing is reduced to a minimum.

In order to feed the charge of solid composition from the movable chamber into the melting vessel, piston or like means may be employed which force the charge from the chamber to the vessel when the chamber is in the feeding position. The piston employed for this purpose may be disposed always in alignment with the inlet passage to the melting vessel, or it may be arranged to move with the movable chamber, being housed in a cylinder secured to or forming part of the chamber element, 1. e. the element in which the movable chamber is formed. In either case it is desirable to provide for the sealing of the passage through which the piston works, to avoid leakage from the melting chamber through said charging. which air might have a deleterious effect it regularly introduced along with the composition into the melting vessel. This largely obviatesthe necessity of supplying the chamber with inert gas under pressure for the purpose of sweeping out the atmospheric air and for the purpose feeding operation and to prevent leakage thereof between the feed operations, and to prevent undue loss of heat from the vessel while the fresh composition is being introduced.

It has now been found that the difiiculties mentioned above can be overcome or substantially reduced, and the spinning of fused thermoplastic compositions may be carried out conveniently and effectively as a continuous operation, by introducing charges of solid composition into a chamber that is movable between a charging position in which said chamber communicates with the atmosphere and in which the melting vessel is closed to the atmosphere, and a feeding position in which the said chamber is closed to the atmosphere and is in communication with the melting vessel. By the provision of a movable chamber of this kind the sealing of the melting vessel and also of the chamber may readily be effected by the contact of sliding surfaces of the element in which the chamber is formed against stationary surfaces, while the number of moving parts inof preventing escape of the inert gas under pressure from the melting vessel into the chamber. The sealing eflected at the sliding surfaces of the chamber element may be maintained by the use of spring or like loading adapted to keep said surfaces in contact with the surfaces with which they engage, with the force necessary for the purpose. If desired, the sealing may be augmented by the use of an additional sealing member interposed between the chamber element and the stationary parts of the machine, in which case the same loading may be employed to hold together the several relatively moving parts involved.

It is generally convenient that the movement of the chamber should be effected by rotation of the chamber element about a spindle, although if desired the element may be arranged to slide without rotation from one of its positions to the other. Thus, in one form of apparatus the chamber may be formed as a cylindrical hole through the depth of a thick disc arranged to rotate about a spindle fixed to the melting vessel in the neighis spring-pressed into a valve body into which the plug fits. Two apertures are provided through the wall of the valve body, one in communication with the melting vessel and the other in communication with the atmosphere, and the bore of the plug communicates alternately with these two openings in the valve body. The other end of the chamber communicates with a cylinder secured to or integral with the plug, and besides constituting a part of the chamber, housing a piston by means of which the composition may be forced into the melting vessel.

Either of the devices described above may b worked manually on a visual indication that fresh composition is required in the melting vessel or automatically in accordance with a mechanical or electrical indication.

The invention is applicable generally to methods of spinning or extruding continuously in which solid composition is to be introduced into a melting vessel at the same time as the molten composition is being drawn from said vessel for spinning or extrusion. It is most advantageous, however, in connection with the methods mentioned above in which an atmosphere of an inert gas under pressure is maintained within the melting vessel since it not only prevents the admission of atmospheric air .into the melting vessel, but also prevents the leakage of insert gas under pressure from the melting vessel, Thus for example the invention may be used in conjunction with the methods and apparatus described in U. S. application S. No. 522,458, filed February 15, 1944, in which the melting in the vessel is effected by feeding the composition through a body of liquid that is maintained at a temperature sufficiently high to melt the composition. While in the body of liquid, the composition may be deflected, as described in U. S. application S. No. 567,062, filed December 7, 1944, towards the walls of the vessel e. g. by means of a domed or conical baiile, to facilitate melting.

In U. S. application Serial No. 522,458 there is described means for obtaining an indication that fresh composition is required in the melting vessel, said means comprising a float on the surface of the body of heating liquid, adapted to make and break an electrical contact as the level of said surface rises and falls. Another and preferred way of obtaining an indication of the level of liquid in the heating zone, and, therefore, of the amount of composition in the melting vessel, is to make use of a temperaturediiference existing between different fluid phases of material in the melting zone, and particularly between a gaseous phase and the liquid phase below it. If heat is supplied to the heating zone by way of its side walls, and the charging and other connections enter the top of the zone, a temperature diiferenceof as much as 20 to 30 C, may exist betweenthe gaseous and the liquid phase. By observing the temperature in the neighborhood of a fixed point within the zone it can be ascertained when the boundary between the phases moves past that point, and the feed of fresh solid composition can be adjusted, preferably automatically, so as to restore the-phase boundary to its former position relatively to that point.

By way of example two forms of apparatus in accordance with the present invention will now be described in greater detail in reference to the accompanying drawings in which Fig. 1 is a sectional side elevation of a meltspinning apparatus employing the principles described in each of the three last mentioned specifications.

Fig. 2 is a front elevation partly in section of the apparatus in Fig. 1,

Fig. 3 is a sectional side elevation of a simpler and manually operated form of feeding device and Figures 4 and 5 are a front elevation and a sectional plan view respectively of the feeding device shown inFig. 8.

The apparatus shown in Figures 1 and 2 comprises a cylindrical steel ves'sel l in the upper part of which is formed the melting chamber which consists of a cavity 2 of cylindrical form at the top and of conical form at the bottom. A pool 3 of molten composition forms in the bottom of the conical part, while the heating liquid 4, by contact with which the composition is melted, fills the rest of the conical part and about half of the cylindrical part. From the apex of the conical part a passage 5 leads to a spinning pump 6, contained in another cavity 1 in the steel vessel, the cavity 1 being packed with copper turnings to give a high heat capacity. The pump 6 forces the molten composition through a filter.

8 and spinning jet 9. The melt chamber is closed by means of a heavy steel cover l0 bolted on the top of the cylindrical vessel, suitable sealing rings ll being provided to prevent leakage,

Through a gland [2 in the middle of the cover I0 passes a valve rod l3 having a coned end which fits the apex at the bottom of the melt chamber 2, thereby permitting the sealing off of the melt chamber 2 from the spinning pump 6. The valve rod I 3 is screw threaded to work in a threaded part M of the cover, and is provided with a hand wheel I5 so that the valve may be opened from outside the melt chamber 2. The rod itself is bored axially from end to end and is screw threaded internally to receive an auxiliary valve rod IS the lower end of which is pointed so as to fit on a conical seat l1 inside the main valve rod l3. Just above the conical seat I! and at a height between the level of the molten composition 3 and the heating liquid 4, the main valve rod I3 is provided with axial passages I8 giving communication from inside the melt chamber 2 to the bore of the rod IS. The auxiliary valve rod IB is also screw threaded and provided with hand wheel l9, and enters the bore of the main valve rod through a pressure gland 20, By these means, the molten composition can be displaced from the pump 6, filter 8 and jet 9 when desired, e. g. for changing the jet or filter, by means of the heating liquid, the main valve being closed and the auxiliary valve opened. Or again the pump can be primed with the heating liquid while the composition is being initially melted, and when a sufllcient pool of molten composition has been formed, the main valve may be opened and the auxiliary valve closed so that the pump is supplied with the composition.

Extending completely across the cylindrical part of the melt chamber and completely submerged in the heating liquid is a conical grid 2| formed of wire mesh, its apex pointing upwards and terminating in a cylinder 22 closely surrounding the valve rod, and its base terminating in a cylinder 23 contacting with the walls of the chamber 2. The grid 2| constitutes a =baflle of the kind described in U. S. application S. No. 567,062, by which the solid composition is deflected towards the walls of the vessel. The vessel l is surrounded by a jacket 24 containing a heating liquid 25. The jacket 24 is externally wound with electrical heating coils 26, by which heat is supplied to the vessel I, and outside the heating coils 26 the walls are covered with heatinsulating material 21 to prevent undue loss of heat.

The melt chamber 2 also contains a level-indicating device in the form of a conical bulb 28 containing mercury or other fluid of suitable thermo-metric properties, and connected at its apex with a capillary tube 29 passing through a gland 36 in the cover Ill. The other end of the capillary tube 29 is connected to an expansible metal bellows 3| filled with mercury for a purpose hereinafter described. The broad base of the conical bulb is disposed at the desired mini-mum level of the heating liquid 4 within the melt chamber 2.

The composition to be melted is fed into the chamber 2 by way of an oblique passage 32 through the cover I8 of the melt chamber, the passage 32 terminating outside the vessel in a flange 33 to which is secured the body 34 of a valve of the conical-plug type. The conical plug 35 of the valve is bored laterally and threaded to receive a cylinder 36, and the valve body 34 is cut-away at 31 to accommodate the cylinder 36 and to allow the conical plug 35, together with the cylinder 36, to be turned from a position in which the cylinder is in alignment with the feed passage 32 through the top of the cover, through an angle of 90 from that position. The valve body 34 is also bored at 38, at an angle of 90 to the feed passage 32, so as to give access to the bore of the cylinder 36 when the feed passage 32 is closed by the valve. This enables sticks of the composition that is to be.fed to the melt chamber 2 to be supplied to the cylinder 36 by being inserted through the bore 38. This is done by means of a dispensing device of known type indicated at 39.

Into the other end of the cylinder is fitted a plunger 40, and round the cylinder is fitted a deep cup 4| to the crown of which the rear end of the plunger 46 is securely attached. The cup 4| is connected, by means of a yoke 42 secured across it, to two connecting rods 43 (Fig. 2) one at each end of the yoke 42.

The other ends of the connecting rods 43 fit on two crank pins 44 mounted in bosses 45 on two gears 46, one on each side of the valve body 34. The ends of the conical plug 35 are reduced so as to constitute a shaft 41 on which the gears 46 are freely mounted. The shaft 41 also carries, inside the gears 46 and close to the valve body 34, two cranks 48, the ends of which are secured to the two ends 49 of a long forked connecting rod 50. The other end of the connecting rod 58 is secured to the sheaf of an eccentric 52 which is freely mounted on a main shaft 53. The two gears 46 are connected to two further gears 54 both secured to a shaft 55 which also carries a sprocket 56, the sprocket 56 being connected by a chain 51 and idler sprocket 58 to a further sprocket 59 freely mounted on the main shaft 53. In addition, one of the crank 48 carries a pawl 66 which engages with the boss 45 on one of the gears 46, so as to drive it in one direction, 1. e. when the plug 35 is moving towards the position in which it communicates with the feed pasage 32. The main shaft 53 is constantly driven and carries two control discs 6|, 62, one in association with the eccentric 52 and the other in association with the sprocket 59. The eccentric 52 and the sprocket 59 are connected at intervals to their respective control discs- 6|, 62 by two clutch means of similar form to one another.

The two clutch means comprise a lever 65, pivoted at 86 on the eccentric 52 and a similar lever 61 pivoted to a disc 68 secured to the sprocket 59. Each lever 65, 61 extends approximately at right angles to the radius on which it is pivoted. The levers 65, 61 carry at their free ends pins 69 extending parallel to the main shaft 53 and each adapted to fit laterally into a semi-circular notch 18 or 1| in the edge of the control disc 6| or 6 2. The outer side of each lever 65, 61 is formed as a ramp 12, curving outwards away from the pivot 01' the lever. The eccentric 52 and disc 68 also carry a second lever on each, 13, 14 respectively, pivoted close to the shaft 53 and extending approximately radially outwards, the end of each lever 13, 14 being turned over at 15 so as to engage outside the ramp 12 on the first lever 65 or 61. Both the levers 65, 13 are loaded by springs (not shown), the first in such a manner that its free end is urged away from the main shaft 53 and the second in such a manner that, when its end 15 presses on the ramp 12 of the first lever 65, it urges the first lever inwards towards the main shaft 53, the second spring being of such strength as to overcome the first. The levers 61, 14 are similarly loaded. On the eccentric 52, at a position about 90 behind the levers 65, 13 is secured a lug 16 that is bent over, parallel to the main shaft and reaching almost to the disc 68, the free end of the lug 16 following the same path .as the end 15 of the lever 14. A similar lug 11 is carried on the disc 68, its end following the same path as the end of the lever 13. The angular positions of these lugs is shown in Fig. 1, but as the lugs would not normally appear in Fig. 2, the lug 11 is shown dotted, out of its true position. 0n the edge of the disc 68 is a notch 18 adapted to be engaged by a pawl 19 secured to the frame 88 of the machine and, in a certain position of the disc 68, to prevent rotation thereof in a sense contrary to that of the main shaft 53. A fixed catch stop 8| secured to the machine frame 88 is adapted to engage the end 15 of the lever 14 of the sprocket clutch mechanism in such a manner that, although the lever 14 can be forced past the stop by the rotation of the sprocket (the lever swinging back against its spring loading), the engagement of the lever with the stop 8| forces the end 15 of the lever out of engagement with the ramp 12 on the first lever 61 and permits the first lever, under the action of its spring, to move outwards and disengage the pin 69 from the, notch 1| in the control disc 62.

The fluid-filled bellows 9|, previously described as being connected to the free end of the capillary tube 29 communicating with the conical bulb 28 within the melt chamber 2, is arranged to act on the short end of a catch lever the other end 86 of which swings into the path of the end 15 of the lever 13 of the eccentric clutch. Contraction of the bellows 3| as a result of cooling the conical bulb 28 in the melt chamber 2 moves the end of the catch lever 85 out of the path of theclutch lever 13. The catch lever 85 is loaded by means of a spring 81 so as to return to its original position on expansion of the bellows 3| when the temperature of the conical bulb 28 is raised. The position of the end of the catch lever 85 is diametrically opposite to the position of the catch stop 8| acting on the second lever 14 of the sprocket clutch mechanism. The two notches 10, 1| in the edges of the control discs 6|, 62 of the two clutches are so placed that the notch 1| controlling the 7 I sprocket clutch is about 90 in lead of the notch 10 controlling the eccentric clutch. A lever 53, operating an eccentric cam 89 engaging with an extension 90 of the lever 85, enables the mechanism to be put into operation independently of the state of the bellows 3| if desired.

The operation of the device is as follows. When the supply of composition in the melt chamber 2 is sufllcient, the heating liquid 4 in the melt chamber is above the base of the conical bulb 28. Both clutches are then disposed so that their second levers I3, 14 are held, lever 13 by the catch lever 85 and the other lever 14 by the catch stop 8|, both first levers 65, 51 are held by their springs with their pins 33 out of engagement with the control discs 82. When, however, the contents of the melt chamber 2 are reduced by the act of spinning to such an extent that the level of the heating liquid 4 drops below the base of the conical bulb 23, the conical bulb is cooled by contact with the atmosphere above the heating liquid 4, which atmosphere is some 20-30 cooler than the heating liquid. In consequence the mercury or the like in the bulb 28 contracts and the metal bellows 3| connected to the bulb by the capillary tube 23 is contracted. This moves the catch lever 85 and frees the second lever 13 of the eccentric clutch, allowing its end 15 to engage the ramp 12 on the first lever 65 and so pressing the pin 59 of the first lever inwards against the edge of the control disc 8|. In due time the notch in the control disc comes round to the pin 59 on the end of the lever 65, whereupon the pin drops into the notch and clutches the eccentric 52 to the control disc iii. The eccentric 52 is thereby driven, and is allowed to rotate through an angle of 180?. In so doing it acts through the eccentric connecting rod 50 to turn the conical plug 35 of the valve through an angle of 90. The pawl '60 carried by the crank 48 connected to the conical plug 35 engages the boss 45 on one of the gears 46 carrying the crank pins 44 which operate the plunger 40, and turns both gears 45 through an angle of 90, with the plug 35. In this way premature actuation of the plunger 40 by relative motion between the plug 35 and the gears 46 is prevented. The rotation of the gears 48 however has the effect of rotating the sprocket 59 on the main shaft 53 alsothrough an angle of 90, and in consequence of this, the lever 14 of the sprocket clutch mechanism is forced past the stationary catch stop 8|- When the eccentric 52 has thus rotatedthrough 180 and the sprocket 59 through 90, the second lever I3 of the eccentric clutch encounters the lug 11 on the disc 58 secured to the sprocket 59 and is forced back, allowing the first lever 55 of the eccentric clutch to spring clear of the control disc GI and to disconnect the eccentric 52 from the control disc 6i. At the same time the first lever 61 of the sprocket clutch, the pin 69 of which has been riding on the edge of its control disc 62, is overtaken by and drops into the semi-circular notch II in its control disc 62. Thus as the eccentric 52 is declutched, the sprocket 59 is clutched to the main shaft 53. The sprocket 58 is thus rotated, also through an angle of 180, thereby driving the gears 45 carrying the crank pins 44 which operate the plunger 40 through the connecting rods 43, and cansing the plunger 40 to execute its inward stroke whereby the rod of composition in the plug J5 and cylinder 35 is forced into the passage 32 leading to the melt chamber 2. At the end of this is declutched.

'8 movement the secondlever 14 of the sprocket clutch mechanism engages the lug 15 secured to the eccentric 52 and the sprocket 53 is disconnected from the main shaft 53 in a manner similar to that previously described with reference to the eccentric clutch. The main shaft 53 then rotates idly for 180, until the notch 10 in the eccentric control discs 8i coincides with the pin 69 of the lever 65. When the notch 10 comes round to its pin 69, the pin drops in and the eccentric 52 is driven for a further 180. This swings the conical plug 35 through an angle of 90 back to its original position. During this motion the gear 46 controlling the plunger 40 is not caused to rotate with the plug 35 since in the first place the pawl 50, which effected the previous motion in the opposite direction, only works one way and in the second place the notch 18 in the edge of the sprocket clutch disc 83 is engaged by the pawl IS on the frame 30 of the machine to prevent backward motion of the sprocket 59 as previously described. In consequence, the movement of the plug 35 causes the piston 40 to be drawn back halfway. At this point the eccentric clutch is again tripped by engagement of its lever 13 with the lug 11 attached to the sprocket clutch disc 53 and ceases to rotate. The eccentric has now reached the original position in which it started, having completed one revolution. At the same time the sprocket clutch is engaged, the notch H in itsv control disc coming round to the pin 59 on the lever 61, and the sprocket 59 is thereby driven for a quarter of a revolution. At the end of this time the lever 14 of the sprocket clutch encounters the fixed catch stop 8! and the sprocket 59 The main shaft 53 then turns through a further 270 before anything further can happen. If the stick of composition fed into the melt chamber 2 in this way is suflicient to raise the level of the heating liquid 4 enough to heat up the conical bulb 23, the catch lever 35 will by this time have been restored to its former position, and the main shaft 53 continues to rotate idly until the level of the liquid in the melt .chamber 2 falls again. If, however, the stick of composition is not sufllcient for this purpose, the catch lever 85 remains in the engaged position so that the eccentric clutch engages and the whole sequence of operations is repeated.

To sum up, the sequence of operations occupies 3 revolutions of the main shaft 53, starting from the time when the eccentric clutch first engages. During the first half-revolution, the eccentric 52 is driven through 180", rotates the plug 35 through from the charging position to the feeding position and also drives the sprocket 53, indirectly and not through the sprocketclutch, through 90. During the second half-revolution the sprocket clutch is engaged and drives the sprocket 59 through thereby effecting the inward stroke of the plunger 40 and the feeding of a stick of polymer to the melt chamber 2. The third half-revolution is idle. During the fourth half-revolution. the eccentric 52 is rotated through 180' thereby returning the plug 35 from the feed to the charging position, the sprocket 59 is stationary, and the plunger 40 executes half its return movement by reason of the relative motion of the plug 35 and the gear 46 operating the plunger 40. During the fifth half-revolution the eccentric 52 is stationary and the sprocket 53 rotates through 90, thereby completing the return stroke of the plunger 40. The latter half of the fifth half-revolution and also the sixth half-revolution are idle. The cycle is then repeated or not according as the catch lever 85 is or is not withdrawn from the position in which it holds the end 15 of the second lever I3 of the eccentric clutch.

In the apparatus shown in Figures 3 to the top of a melting vessel I, with cover I0, is shown, of similar form to that of Fig. 1.

The movable chamber by means of which the composition is charged into the melting vessel I is formed as a cylindrical hole. 95 through the depth of a thick disc or cylinder 95 arranged to rotate about a spindle 91 mounted on a plate 98 which forms an eccentric flange to the inlet passage 99 of the vessel I. The passage 99 and flange 98 are formed integral with the cover I0 of the vessel I.

Between the flange 98 and the cylinder 96 is a cylinder 96 and cover I04 are hardened and ground so as to form a satisfactory seal.

thin steel disc I00 provided with a handle IOI by means of which it may be rotated about the spindle 91. The disc I 00 has a hole I02 which may be brought into alignment with the passage 99 by means of the handle IOI, a stop I03 being provided on the flange 98 to locate the hole I02 in this position. Above the cylinder 96 is a cover I04 splined at I05 to the spindle 91 and pressed down by means of a powerful spring I08 and nut I09 so as to clamp the disc I00 and cylinder 95 against the flange 98.

Rising from and integralwith the cover I04 is a cylindrical member IIO housing a piston III that is in constant alignment with the inlet passage 99 to the vessel I. The upper part of the piston I I I is enlarged at II 2 to fit the upper part of the cylindrical member IIO while the lower part of the piston III is of the same diameter as the chamber 95, the bore of the inlet passage 99, and the bore of the lower part of the cylinder I I0. The shoulder II4 between the larger and the smaller part of the piston III fits on an annular seat H5 in the cylindrical member IIO so as to form a seal when the piston is in its lower position. The piston is operated by means of a lever II6 pivoted at III to a link II8 which in turn is pivoted at II9 to an extension I of the flange 98.

The cylinder 95 is provided with a handle I2I and with an upwardly extending block I 22 adapted to engage with either of two stops I23, I24, on the edge of the cover I04. When the block I22 is against the stop I23, the chamber 95 is in alignment with the cylindrical portion H0 and the passage 99. When the block I22 is against the stop I24, the chamber 95 is in alignment with a charging hole I25 in the cover I04.

In operation, the thin disc I00 is, for the greater' part of the time, in the position shown in Figures 3-5 so that it seals the inlet passage 99, while the block I22 is against the stop I24. When it is desired to feed composition into the vessel I a cylindrical stick of the composition adapted to fit the chamber 95 is inserted into the chamber through the hole I25 in the cover I04. The cylinder 96 is then rotated against the stop I 28 so as to bring the chamber 95 in alignment with the passage 99. The disc I00 is then rotated by means of the handle IOI against the stop I08 and the handle H6 is forced down so that the piston III forces the stick of composition into the vessel 1 and the shoulder II4 seats against the seating I I5. The handle I M is then rotated away from the stop I03 so as to seal the passage 99, the handle I I6 is lifted and the cylinder 96 rotated to the supply position. The cylinder 96 is made of cast The invention is applicable generally to the spinning or extrusion of organic filament-forming compositions that may be spun in the molten state and is particularly advantageous where, as is commonly the case with such compositions, the compositions are liable to decompose or be otherwise iniuriously afiected at temperatures not much exceeding those necessary to melt them. Examples of such compositions are the synthetic linear superpolyamides made, e. g. by the condensation of diamines with dicarboxylic acids. Or the compositions employed may have a basis of a polyvinyl compound, e. g. polymerized vinylidenechloride, or a copolymer of vinyl chloride and vinyl acetate. Or again the invention may be applied to compositions having a basis of cellulose derivatives, such as organic esters (including mixed esters) of cellulose, ,e. g. cellulose acetate, cellulose propionate and cellulose butyrate, cellulose acetate-butyrate, cellulose acetate-propionate or cellulose acetate-stearate, or cellulose ethers such as ethyl and benzyl cellulose.

Having described our invention, what we desire to secure by Letters Patent is:

1. Method of extruding fusible filament-forming materials, said method comprising melting the material in a confined space containing a gaseous atmosphere at superatmospheric pressure by contact in said space with a liquid heating medium inert to and of lower density than the material, maintaining a supply of solid material in a cavity within a body whose surface forms one boundary of said confined space, withdrawing fused material from below the surface of said heating medium within said space and extrudin the material withdrawn, detecting the temperature at a fixed level within said space and, when ever a sharp temperature change indicates that the surface of said heating medium has fallen below said level, moving said body so as to bring said cavity into communication with said space so as to feed the solid material in said cavity into said space and temporarily to raise said surface and reverse said temperature change.

2. Apparatus for the extrusion of fused thermoplastic filament-forming materials, said apparatus comprising a melting vessel, means for withdrawing fused material from said vessel for extrusion, and feed means for maintaining a supply of material in said vessel, said feed means comprising a feeding member having a feed cavity therein and a piston adapted to work in said cavity to expel solid material therefrom, said feeding member being movable to and from a charging position in which said feed cavity communicates with the atmosphere for the reception of solid material, through a sealing position in which said cavity is closed to the atmosphere and to said vessel respectively from and to a feeding position in which said cavity is open only to said vessel to permit the transfer of solid material by said piston to said vessel, said vessel being at all times closed to the atmosphere by said feeding member.

3. Apparatus for the extrusion of fused thermoplastic filament-forming materials, said apparatus comprising a melting vessel, means for withdrawing fused material from said vessel for extrusion, and feed means for maintaining a. supply of material in said vessel, said feed means comprising a rotatable conical plug, a hollow cylinder extending laterally from said plug. a piston and piston rod in said cylinder, 9. deep cup.

11 fitting outside and sealing the free end of said cylinder and secured at its closed end to said piston rod, and a housing for said Plug forming part of said melting vessel and cut away to accommodate said cylinder, said plug having a lateral bore that forms an extension of the bore of said cylinder the combined bore of said plug and said cylinder communicating in one position of said plug with a hole in said housing for the supply of solid material to said bore, and in another position only with a hole in said vessel for the transfer of solid material by said piston to said vessel, and in an intermediate position being completely sealed, the hole in said vessel being at all times closed to the atmosphere by said plug.

4. Apparatus for the extrusion of fused thermoplastic filament-forming materials, said appar tu c mpri n a melting vessel, means for withdrawing fused material from said vessel for extrusion, and feed means for maintaining a supply of material in said vessel, said feed means comprising a, rotatable conical plug, a crank and connecting rod for rotating said plug to and fro between end positions, a hollow cylinder extending laterally from said pl a piston and a piston rod in said cylinder, 9. deep cup, fitting outside and sealing the free end of said cylinder and secured at its closed end to said piston rod, a crank and connecting rod for driving said piston by means of said cup and piston rod, a housing for said plug forming part of said melting vessel and cut away to accommodate said cylinder, said plug having a lateral bore that forms an extension of the bore of said cylinder the combined bore of said plug and said cylinder communicating in one end position of said plug only with a hole in said housing for the supply of solid material to said bore, and in the other end position only with a hole in said vessel for the transfer of solid'material by said piston to said vessel. and in an intermediate position being completely sealed, the hole in said vessel being at all times closed to the atmosphere by said plug and intermittent driving means for said cranks, mutually timed so as to work said piston through the bore in said plug to eife ct said transfer when said plug is stationary in the second-mentioned end position.

5. Apparatus for the extrusion of fused thermoplastic filament-forming materials, said apparatus comprising a melting vessel, means for withdrawing fused material from said vessel for extrusion, means for detecting the quantity of material in said vessel, feed means for maintaining a supply of material in said vessel and actuating means for said feed means under the control of said detecting means, said feed means comprising a rotatable conical plug, a crank and connecting rod for rotating said plug to and fro between end positions, a hollow cylinder extending laterally from said plug, a piston and piston rod in said cylinder, a deep cup, fitting outside and sealing the free end of said cylinder and secured at its closed end to said piston rod, a crank and connecting rod for driving said piston by means of said cup and piston rod, a housing for said plug forming part of said melting vessel and cut away to accommodate said cylinder, said plug having a lateral bore that forms an extension of the bore of said cylinder the combined bore of said plug and said cylinder communicating in one end position of said plug only with a hole in said housing for the supply of solid material to said bore, and in the other end position only with a hole in said vessel for the transfer of solid material by said piston to said vessel, and in an intermediate position being completely sealed, the hole in said vessel being at all times closed to the atmosphere by said plug and intermittent driving means for said cranks, actuated under the control of said detecting means whenever the quantity of the material detected falls below a predetermined quantity and mutually timed so as to work said'piston through the bore in said plug to effect said transfer when said plug is stationary in the second-mentioned end position.

, 6; Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly 'filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, means for introducing solid material into said vessel, and temperaturesensitive means within said vessel for detecting temperature changes at a fixed level therein, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, said temperature-sensitive means being operatively connected to said means for introducing solid material into said vessel.

7. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, temperature-sensitive means within said vessel for detecting tempera- 40 ture changes 'at a fixed level therein, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, feed means for supplying solid material into said vessel and operating means for said feed means under the control of said temperature-sensitive means and adapted to be actuated thereby whenever a sharp temperature change occurs as the surface of said medium falls below said level.

8. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, means for introducing solid material into said vessel, and a conical liquid-filled bulb within said vessel having a liquidfllled stem extending from said vessel and having its base at a fixed level for detecting temperature changes in said vessel at said level, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, said means for detecting temperature changes in said vessel being operatively connected to said means for introducing solid material into said vessel.

9. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, 9, heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, means for introducing solid material into said vessel, a conical liquid-filled bulb within said vessel, a liquid-filled bellows outside said vessel and a liquid-filled tube connecting said bulb and bellows, said bulb having its base at a fixed level in said vessel for detecting, by the distension of said bellows temperature changes at said level, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, said means for detecting temperature changes in said vessel being operatively connected to said means for introducing solid material into said vessel.

10. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the materials, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding .the material so withdrawn, a conical liquid-filled bulb within said vessel, a liquid-filled bellows outside said vessel and a liquid-filled tube connecting said bulb and bellows said bulb having its base at a fixed level in said vessel for detecting by the distension of said bellows temperature changes at said level, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, feed means for supplying solid material into said vessel and operating means for said feed means under the control of said bellows and adapted to be actuated by the distension thereof whenever a sharp temperature change occurs as the surface of said medium falls below said level.

11. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused mate-, rial from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn. a feeding member that is movable to and from a charging position in which a feed cavity in said member communicates with the atmosphere for the reception of solid material through a sealing position in which said cavity is closed to the atmosphere and to said vessel respectively from and to a feeding position in which said cavity is closed to the atmosphere and communicates with said vessel to permit the transfer of solid material to said vessel, said vessel being at all times closed to the atmosphere by said feeding member, and temperature-sensitive means within said vessel for detecting temperature changes at a fixed level therein, the volume of said medium being lessthan the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, said means for detecting temperature changes in said vessel being operatively connected to said feeding member.

12. Apparatus for extruding fusible-filamentforming materials, said apparatus comprising a melting vessel in which to. fuse the material, a

heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, a rotatable conical plug,

a hollow cylinder extending laterally from said plug, a piston and piston rod in said cylinder, a deep cup fitting outside and sealing the free end of said cylinder and secured at its closed end to said piston rod, a housing for said'plug forming part of said melting vessel and cut away to accommodate said cylinder, said plug having a lateral bore that forms an extension of the bore of said cylinder and communicates in one position of said plug with a hole in said housing for the supply of solid material to said bore, and in another position with a hole in said vessel for i the transfer of solid material by said piston to at all times closed to the atmosphere by said plug, and temperature-sensitive means within said vessel for detecting temperature changes at a fixed level therein, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel. I

13. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material-from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, a feeding member that is movable to and from a charging position in which a feed cavity in said member communicates with the atmosphere for the reception of solid ma terial, through a sealing position in which said cavity is closed to the atmosphere and to said vessel, respectively from and to a feeding position in which said cavity is closed to the atmosphere and communicates with said vessel to permit the transfer of solid material to said vessel, said vessel being at all times closed to the atmosphere by said feeding member, temperaturesensitive means within said vessel for detecting temperature changes at a fixed level therein, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, and operating 7 means for moving said feeding member under the control of said temperature-sensitive means and adapted to be actuated thereby whenever a sharp temperature change occurs as the surface of said medium falls below said level.

14. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling" said vessel. and in an intermediate position with neither of said holes, the hole in said vessel bein at all times closed to the atmosphere by said plug, temperature-sensitive means within said vessel for detecting temperature changes at a fixed level therein, the volume of said medium being less than the volume of the part ofsaid vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, and operating means for rotating said plug under the,control of said temperaturesensitive means and adapted to be actuated thereby whenever a sharp temperature change occurs as the surface of said medium falls below said level.

15. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the material, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the material so withdrawn, a rotatable conical plug, a housing therefore forming part of said melting vessel said plug having a lateral bore communicating in one position of said plug with a hole in said housing for the supply of solid material to said bore, and in another position with a hole in said vessel for the transfer of solid material to said vessel, and in an intermediate position with neither of said holes, the hole in said vessel being at all times closed to the atmosphere by material so withdrawn, a conical liquid-filled bulb within said vessel, a liquid-filled bellows outside said vessel and a liquid-filled tube connecting said bulb and bellows, said bulb having its base at a fixed level in said vessel for detecting, by the distension of said bellows temperature changes at said level, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, a rotatable conical plug, a crank and connecting rod for rotating said plug to and fro between end positions, a hollow cylinder extending laterally from said plug, a piston and piston rod in said cylinder, 9, deep cup fitting outside and sealing the free end of said cylinder and secured at its closed end to said piston rod, a crank and connecting rod for driving said piston by means of said cup and piston rod, 3, housing for said plug forming part of said melting Y vessel and cut away to accommodate said cylinder,

said plug. a conical liquid-filled bulb within said vessel, a liquid-filled bellows outside said vessel, a liquid-filled tube connecting said bulb and bellows, said bulb having its base at a fixed level in said vessel for detecting, by the distension of said bellows, temperature changes at said level, the volume of said medium being less than the volume of the part of said vessel below said level by an amount equal to the volume of the material it is desired to maintain in said vessel, and operating means for rotating said plug under the control of said bellows and adapted to be actuated by the distension thereof whenever a sharp temperature change occurs as the surface of said medium falls below said level.

16. Apparatus for extruding fusible filamentforming materials, said apparatus comprising a melting vessel in which to fuse the materials, a heating medium inert to said material and liquid at the melting temperature thereof partly filling said vessel, means for withdrawing fused material from below the surface of said heating medium within said vessel, means for extruding the said plug having a lateral bore that forms an extension of the bore of said cylinder and communicates, in one end position of said plug with a hole in said housing for the supply of solid material to said bore, and in the other end position with a hole in said' vessel for the transfer of solid materialby said piston to said vessel, and in an intermediate position with neither of said holes, the hole in said vessel being at all times closed to the atmosphere by said plug, and intermittent driving means for said cranks under the control of said bellows and adapted to be actuated by the distension thereof whenever a sharp temperature change occurs as the surface of said medium falls below said level, said driving means being mutually timed so as to work said piston through the bore in said plug to effect said transfer when said plug is stationary in the second-mentioned end position.

ROBERT WIGHTON MONCRIEFF. WILLIAM POOL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,437,704. March 16, 1948.

ROBERT WIGHTON MONCRIEFF ET AL. It is hereby certified that error appears in the rinted specification of the above numbered patent requiring correction as follows: (golumn 11, line 9, claim 3, after plug insert the word only; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 18th day of May, A. D. 1948.

THOMAS F. MURPHY,

'Auidmt (Zommfadoner of PM. 

